Known continuous wave (CW) fiber lasers are used in industrial applications such as marking, medal cutting, welding, and the like. CW fiber lasers are suitable for industrial applications because of their high wall-plug efficiency and output beam quality. Additionally, a single strand of a CW fiber laser can output power in the kilo-Watt level.
The power and brightness of CW fiber lasers can be scaled by combining multiple CW fiber lasers via coherent arrays. Specifically, the power output can be increased by combining the output of multiple CW fiber lasers coherently. To produce a coherent array, the multiple coherent lasers are added in-phase. This can be accomplished using either active phase control or passive phasing.
Passive phasing combines multiple CW fiber lasers using spontaneous phase locking. The coherent coupling efficiency of a passive coherent array produced by combining multiple CW fiber lasers depends on the spectral bandwidth of each laser to be combined. Lasers having large spectral bandwidths can be more effectively combined than lasers having respectively smaller spectral bandwidths. Accordingly, a need exists for a passive coherent array having multiple fiber lasers with increased spectral bandwidths.